1. Field of the Invention
The present invention relates to a printer and a printing method.
2. Description of the Related Art
In printing results of documentation, accounting and statistics, diagrams, lists and slips having frames formed with lines are widely used. Characters to be printed in the frames generally vary from page to page, but the frames will not vary. In printing such diagrams and lists, therefore, data of a fixed form (hereinafter referred to as form data) is stored in a memory for repeated use. A process is performed to synthesize the form data and data to be inserted into frames (hereinafter referred to as non-form data). The synthesizing process is called a form overlay process.
A conventional form overlay process will be described taking a case where data shown in FIG. 1 is transmitted from a host computer by way of example. When supplied to a printer, form data T1 (code data) is stored in a form data memory in the printer. The form data is developed in a form data image memory. A form overlay print instruction is next supplied from the host computer to the printer. By this instruction the printer is set to a form overlay print mode. Subsequently the first page of the non-form data is supplied from the host computer to the printer. The non-form data is temporarily stored in a receiving buffer. The non-form data is read out of the receiving buffer to be developed in a non-form data image memory. Afterward bit map data recorded in the form data image memory are logical ORed with bit map data recorded in the non-form data image memory. The resulting bit map data are written into a frame memory. When a print image for one page is prepared in the frame memory, the image is printed on a sheet of paper. When printing of the first page is completed, the bit map image in the frame memory is cleared (erased).
When non-form data for the second page is applied to the printer, it is developed in the non-form data image memory. The contents of the form data image memory are logical ORed with the contents of the non-form data image memory. The results of logical ORing are stored in the frame memory. When the image data for one page is developed in the frame memory, printing operation is carried out. Upon the completion of printing, the contents of the frame memory are cleared. The above processes are subsequently repeated each time non-form data for the next page (the third page, fourth page, etc.) is supplied from the host computer.
With the conventional form overlay process, the non-form data and the form data are synthesized or combined and developed each time the non-form data is changed. Therefore, problems with the conventional printer are slow printing speed and low printing efficiency for images having frames. Moreover, two memories (or two areas) for bit map data are needed in addition to frame memories.